How long should we be allowed to go past our due date?

I have read it somewhere that usually about ten days. Pregnancy is two hundred eighty days, or forty weeks, from the last menstrual period, or two hundred sixty-six days from conception. However, “term” is considered thirty-eight to forty-two weeks. It is also 2 weeks after or before the estimated date of delivery during your 1st ultrasound. Hope this helps.